A. Technical Field
The present invention relates generally to impedance transformation within an electrical circuit, and more particularly, to the application of bulk acoustic wave (hereinafter, “BAW”) technology to provide impedance transformation and filtering functionality within a resonator network.
B. Background of the Invention
The importance of impedance matching within an electrical circuit is well understood within the art. Impedance matching relates to the concept of optimizing a source impedance equal to a target load impedance in order to efficiently deliver a signal from source to load. In particular, the output load impedance seen by a power amplifier should be chosen to optimize the efficiency of that amplifier. This principle of impedance matching is important to numerous technology applications and markets, and the design of electrical circuits therein.
The wireless and Radio Frequency (“RF”) market is an example in which impedance matching and transformation is very important in the design of electrical circuits. In fact, the high frequency RF signal may be sensitive to impedance mismatches within an electronic circuit. Electrical component characteristics (e.g., wire inductances, transistor parasitics, interlayer capacitances and conductor resistances) may significantly impact the design of impedance matching elements used to connect these components, or the blocks in which they reside, in a circuit. The design and implementation of a proper impedance matching network within an RF circuit is oftentimes very complex and may require significant cost and board or module area in its implementation.
FIG. 1 illustrates exemplary transmit and receive signal paths within an RF environment. As illustrated, a transmit driver 110 is coupled to a bandpass filter 120 via a first matching element 115. The bandpass filter 120 is coupled to a power amplifier 130 via a second matching element 125. The power amplifier 130 is coupled to a duplexer 150 via a third matching element 143 and a fourth matching element 146.
On the receiver path, the duplexer 150 is coupled to a low noise amplifier 160 via a fifth impedance matching element 155. The low noise amplifier 160 is coupled to a bandpass filter 170 via a sixth matching element or 165. The bandpass filter 170 is coupled to other components within the receiver signal path via a seventh matching element 175.
These matching elements provide an impedance transformation between the components in the electrical circuit. For example, in an RF environment, impedance matching elements may provide an impedance step-up from 3Ω to 50Ω between various components or an impedance step-down from 50Ω to 30Ω depending on which components are being coupled. For example, the third matching network 143 and the fourth matching network 146 may provide such an impedance transformation of 3Ω to 5Ω at the power amplifier 130 output to 50Ω at the duplexer input 150. One skilled in the art will recognize that impedance matching elements may be used to match numerous different impedance values and that a particular impedance transformation may be provided by a single impedance element or multiple impedance elements in various configurations.
The design and implementation of impedance matching impedance elements may significantly increase the complexity of an electrical system and require additional board area and cost in the realization of the system itself. Oftentimes, certain components within an electrical system may need to be located “off-chip” in order properly match the component within the system. These off-chip components provide high “Q” characteristics and very good transformation loss between components. However, the off-chip components also require additional board or module space in their implementation. For example, the design of an electrical circuit may require that one or more impedance matching elements be located outside of an integrated circuit for various reasons including size considerations of the matching element(s), interfacing with out off-chip components, etc. FIG. 2 illustrates one such example of an RF system having off-chip components located on a board and connected to an integrated electrical circuit by one or more matching elements.
FIG. 2 is intended to illustrate one possible scenario related to the RF system shown in FIG. 1. As illustrated, a bandpass filter 230 in the transmit signal path of the RF system is separate from an integrated circuit 220 and located on a radio board 210. The bandpass filter 230 is coupled within the signal path in the integrated circuit by a first matching element 235 and a second matching element 240. A duplexer 250 is coupled to the transmit signal path by a third matching element 255 and to the receiver path by a fourth matching element 260.
One skilled in the art will readily recognize the added complexity and board or module area required to properly couple separate electrical components (e.g., the integrated circuit 220, the bandpass filter 230 and the duplexer 250) using distinct matching elements. Furthermore, the manufacturing costs associated with the electrical systems increase reflected by the fact that the components must be manufactured separately and each installed onto the board 210.